Shark data recorded since 1972 reveals long term trends

Ask any scientist about the importance of long term data sets and you’ll probably hear the same answer every time: data collected over a long period of time allows you to spot trends and track changes that don’t develop immediately. They are developments that occur over time and simply aren’t easy to spot right away. That’s why the shark surveys that researchers conduct off the coast of North Carolina are so important.

That long term data has recorded the changes in the shark species swimming off the coast. I reported a story about the survey conducted by scientists with the University of North Carolina Institute of Marine Sciences in Beaufort. They’ve been catching, measuring, and then releasing sharks off the coast of Morehead City since 1972. To give you an idea how a shark survey works, here’s a link to the story.

Warming waters lead to more bull sharks

Researchers working on another shark survey near Pamlico Sound report gradually warming ocean waters appear to be driving nursing bull sharks into Pamlico Sound. And that’s an ominous prediction for people. That’s because bull sharks can grow to more than 10 and a half feet long and are know to attack large prey, including humans.

Only six bull sharks were captured in Pamlico Sound from 2003-2011. There were 53 bull sharks captured from 2011 to 2016.

“What we see in Pamlico Sound appears to be a threshold response,” said Charles Bangley, Ph.D., a postdoctoral researcher at the Smithsonian Environmental Research Center. “As southern waters grow warmer, Bull Sharks are shifting their range north, and the warmer temperatures in Pamlico Sound are similar to other estuaries where Bull Sharks are known to give birth.”

The report also says bull sharks can tolerate brackish and fresh waters, which means they could be found in any body of water connected to the ocean.

The study also suggests bull sharks may increase their use of Pamlico Sound as a nursery if ocean temperatures continue to warm and the female sharks born in the system now reach maturity and return to give birth. The study is published in Scientific Reports. It is based on shark catch data collected by the North Carolina Division of Marine Fisheries. Researchers from NCDMS, East Carolina University and Simon Fraser University analyzed the data.

Here's a look at what other sharks are commonly found in the state, from NC Sea Grant's Coastwatch Magazine.

—Frank Graff

Frank Graff is a producer/reporter with UNC-TV, focusing on Sci Tech Now North Carolina, a weekly science series that airs Tuesdays on UNC-TV. In addition to producing these special segments, Frank will provide additional information related to his stories through this North Carolina Science Now Reporter's Blog!